The present invention relates to apparatus and methods for effecting ultrasonic bonding on at least one web or workpiece (or discrete pieces on a workpiece segment or workpiece segments) using ultrasonic bonding apparatus. The invention more particularly concerns apparatus and methods for ultrasonically bonding at least one web or workpiece (or discrete pieces on a workpiece segment or workpiece segments) using rotary ultrasonic bonding apparatus.
Bond strength, where a rotary ultrasonic horn and a rotary anvil are used to bond workpiece segments (or discrete pieces on a workpiece segment or workpiece segments), is dependent on a variety of factors including horn frequency, horn amplitude, dwell time in the nip, and horn/anvil nip loading. More specifically, the consistency and quality of the bond when using such rotary bonding techniques is dependent on the consistency of the force exerted on the workpiece segment by the combination of the anvil roll and the ultrasonic horn: the time during which the workpiece segment is being pressed in the constrictive nip which is dependent on e.g. the operating speed: and the types of materials being bonded. The consistency and quality of the bonds are also dependent on the frequency and amplitude of the vibrations of the ultrasonic horn.
Consistency and quality of bonds when using conventional rotary ultrasonic bonding methods and apparatus have been particularly variable where the desired bond pattern is intermittent because the nip pressures inherently change in concert with the intermittent nature of the bonding operation.
Under excessive loading, so much energy may be applied to the materials being bonded as to burn through or otherwise excessively soften the materials being bonded, as well as to apply excessive pressure to the softened materials, whereby bonds so formed may be weak, and/or may be uncomfortably harsh to the touch of a wearer""s skin. In the alternative, excessive loading can physically damage, as by tearing, the material being bonded. Additionally, excessive loading can increase wear and/or coin and thus damage the ultrasonic horn.
Early practice in the art of ultrasonic bonding was to force an anvil against a horn with a fixed, defined load. The anvil rode on the horn much like a train wheel runs on a rail. The force was constant regardless of the presence or absence of material in the horn/anvil nip. The constant force of the fixed load design at high force levels tended to cause rapid horn wear.
A step in the evolution of ultrasonic bonding was to load an anvil with high force against a fixed stop and to use the stop to set horn/anvil interference. In this design, the stop drew most of the load until material entered the horn/anvil nip; at that point, the greater interference caused by the material drew more of the load as the stop load diminished.
A need exists to develop a horn/anvil nip that can be loaded to a known force rather than a fixed interference. Similarly, a need subsists to develop horn/anvil loading apparatus which can produce a nip load reading representative of force in the nip rather than an inferred value based on theoretical interference.
It is an object of this invention to provide ultrasonic bonding apparatus and methods wherein horn/anvil nip pressure is more consistent along the lengths and widths of respective bonding regions.
It is another object of this invention to provide ultrasonic bonding apparatus and methods wherein force representative of force exerted at the horn/anvil nip can be detected and managed.
It is yet another object of this invention to provide ultrasonic bonding apparatus and methods wherein nip loading information is output from the ultrasonic bonding apparatus and is relayed to a display, therefore allowing an operator to manually or otherwise adjust the ultrasonic bonding apparatus to effect suitable bonding in the horn/anvil nip.
In a first family of embodiments, the invention comprehends ultrasonic bonding apparatus for creating ultrasonic bonds in sequentially advancing absorbent article workplace segments, in a bonding nip. The ultrasonic bonding apparatus comprises a frame, anvil support apparatus, horn support apparatus, closure apparatus, a load cell support member, and a load cell. The anvil support apparatus defines an anvil loading assembly connected to the frame, and supporting an anvil roll having an operating width and a circumference, and mounted for rotation about a first axis. The horn support apparatus is connected to the frame, and supports a rotary ultrasonic horn mounted for rotation about a second axis, substantially aligned with the first axis. The ultrasonic horn and the anvil roll collectively are mounted and configured such that the ultrasonic horn and the anvil roll can be brought together to define the nip therebetween, wherein the anvil roll and the ultrasonic horn rotate in common with each other and with movement of workpiece segments through the nip. The closure apparatus is adapted to bring the anvil roll and the ultrasonic horn together to form the bonding nip. The load cell support member is connected to the frame, and the load cell is mounted to the load cell support member such that force representative of force exerted on the anvil roll at the nip can be detected by the load cell.
The apparatus preferably includes apparatus defining a limit to downward travel of the anvil roll.
In preferred embodiments, the second axis has an orientation parallel to the first axis.
In preferred embodiments, the frame, the anvil support apparatus, and the horn support apparatus collectively provide support structure sufficiently rigid that the horn and the anvil roll can be brought together with optional interference between the horn and the anvil roll of no more than about 0.003 inch in combination with defining sufficient nip pressure to develop ultrasonic bonds in absorbent article workpiece segments passing through the nip.
In some embodiments, a nip width, useful for applying forces to an absorbent article workpiece in the nip, can be defined between the ultrasonic horn and the anvil roll, wherein the anvil support apparatus preferably includes a resilient support member defining a resistance, to movement of the anvil roll away from the nip, of at least about 400 pounds per inch width of the nip.
The anvil support apparatus can further comprise one or both a lifting plate for lifting and lowering the anvil loading assembly with respect to the ultrasonic horn, and a pivot plate pivoting the anvil loading assembly about a third axis oriented perpendicular to the first axis.
In some embodiments, the ultrasonic bonding apparatus includes a back-up roll mounted for surface-to-surface relationship with the ultrasonic horn opposite the nip between the ultrasonic horn and the anvil roll, wherein the back-up roll engages an outer surface of the ultrasonic horn in alignment with extensions of the first and second axes.
In some embodiments, the ultrasonic bonding apparatus includes an adjusting device, operating on a cradle arm, for adjusting a height of the back-up roll, and thus generally defining an upper limit to movement of the ultrasonic horn.
In some embodiments, the ultrasonic bonding apparatus includes first and second support rolls releasably supporting opposing sides of an outer surface of the ultrasonic horn, an imaginary line connecting axes of the first and second support rolls passing vertically below the second axis.
In preferred embodiments, the anvil roll comprises a first relatively smaller radius portion extending about a first portion of a circumference of the anvil roll, and a raised bonding portion comprising a second relatively larger radius, extending about a second portion of the circumference of the anvil roll.
The second radius can be about 0.01 inch to about 0.07 inch larger than the first radius.
In some embodiments, the ultrasonic bonding apparatus includes drawing apparatus, adapted to draw the workpiece segments across the anvil roll, and thus through the nip defined between the anvil roll and the ultrasonic horn, at a speed of at least about 40 feet per minute, preferably at least about 600 feet per minute, and more preferably at least about 1000 feet per minute.
In some embodiments, an operating surface of the anvil roll comprises an array of projections thereon extending around the circumference of the anvil roll, and across the entirety of the transverse width of the anvil roll, thereby covering substantially the entirety of the operating surface of the anvil roll, whereby ultrasonic bonding can be effected at the projections over the entirely of the operating surface.
In other embodiments, an operating surface of the anvil roll comprises an array of projections thereon disposed in discrete spaced arrays which cover portions but not all of the circumference of the operating surface of the anvil roll, whereby ultrasonic bonding can be effected at the projections between the rotary ultrasonic horn and the anvil roll.
In some embodiments, the load cell support member is connected to the horn support apparatus.
In other embodiments, the horn support apparatus comprises a second load cell support member, and a second load cell, mounted to detect a parameter representative of horn loading at the nip.
In preferred embodiments, a force exerted on the anvil roll at the nip, of at least about 400 pounds per inch width of the nip, can be detected by the load cell.
Preferred embodiments include a controller controlling operation of the ultrasonic bonding apparatus, information output from the load cell to the controller being sufficient to enable the controller to provide suitable guidance for adjusting the closure apparatus to effect suitable bonding in the bonding nip.
In a second family of embodiments, the ultrasonic bonding apparatus comprises a frame, anvil support apparatus, horn support apparatus, closure apparatus, optionally a back-up roll, a load cell support member, and a load cell. The anvil support apparatus defines an anvil loading assembly connected to the frame, and supports an anvil roll having an operating width and a circumference, and mounted for rotation about a first axis. The horn support apparatus is connected to the frame, and supports a rotary ultrasonic horn mounted for rotation about a second axis, substantially aligned with the first axis. The ultrasonic horn and the anvil roll collectively are mounted and configured such that the ultrasonic horn and the anvil roll can be brought together to define the nip therebetween, wherein the anvil roll and the ultrasonic horn rotate in common with each other and with movement of workpiece segments through the nip. The closure apparatus is adapted to bring the anvil roll and the ultrasonic horn together to form the bonding nip. The optional back-up roll is mounted for surface-to-surface relationship with the ultrasonic horn opposite the nip between the ultrasonic horn and the anvil roll, wherein the back-up roll engages an outer surface of the ultrasonic horn in alignment with extensions of the first and second axes. The back-up roll includes an adjusting device, for adjusting a height of the back-up roll, and thus generally defines an upper limit to movement of the ultrasonic horn. The load cell support member is supported from the frame, and the load cell is mounted to the load cell support member such that force representative of force exerted on the ultrasonic horn at the nip can be detected by the load cell.
Some preferred embodiments include lifting apparatus defining a limit to downward travel of the anvil roll.
In preferred embodiments, first and second support rolls can be mounted to the horn support apparatus through a horn support plate and a corresponding activation assembly. The horn support apparatus can further comprise equalizer arms mounted to the horn support plate, and equalizing movement of the first and second support rolls, toward and away from the outer surface of the ultrasonic horn.
In some embodiments, the anvil roll support apparatus also comprises a load cell support member, and a corresponding second load cell supported thereby, the second load cell detecting forces representative of forces exerted on the anvil roll at the nip.
A force exerted on the ultrasonic horn at the nip, of at least about 400 pounds per inch width of the nip, can be detected by the load cell.
In a third family of embodiments, the invention comprehends a method of creating ultrasonic bonds in sequentially advancing absorbent article workpiece segments. The method comprises passing the absorbent article workpiece segments through a bonding nip defined by an anvil roll and a rotary ultrasonic horn, activating ultrasonic energy to the horn and creating ultrasonic bonds in workpiece segments passing through the nip, and using a load cell to detect force representative of force exerted on the anvil roll at the nip. The anvil roll and ultrasonic horn are supported by a frame, anvil support apparatus defining an anvil loading assembly connected to the frame, and supporting the anvil roll which has an operating width and a circumference, and is mounted for rotation about a first axis, horn support apparatus connected to the frame and supporting the rotary ultrasonic horn, which is mounted for rotation about a second axis, substantially aligned with the first axis, and closure apparatus adapted to bring the anvil roll and the ultrasonic horn together to form the bonding nip. A load cell support member is connected to the frame, and the load cell is mounted to the load cell support member such that force representative of force exerted on the anvil roll at the nip is detected by the load cell. The method includes rotating the ultrasonic horn and anvil roll in common with each other and with movement of the workpiece segments through the nip, and thereby applying pressure to the workpiece segments in the nip, and correspondingly creating ultrasonic bonds in the workpiece segments passing through the nip.
In some embodiments, the method includes applying first and second support rolls to sides of the ultrasonic horn and lifting the ultrasonic horn into engagement with a back-up roll aligned with the first and second axes such that the first and second support rolls, in combination with the back-up roll, define a fixed operations location for bonding using the ultrasonic horn.
The method can include applying the first and second support rolls to the sides of the ultrasonic horn at locations vertically below the second axis, and urging the first and second support rolls against an outer operating surface of the ultrasonic horn and thereby lifting the ultrasonic horn into engaging relationship with the back-up roll.
In preferred embodiments, the method includes, prior to lifting the ultrasonic horn into engagement with the back-up roll, moving the back-up roll to a sag distance of the ultrasonic horn such that upon the horn being lifted into engagement with the back-up roll, substantially all longitudinal sag is removed from the ultrasonic horn and a horn shaft extending along the second axis.
Typically, the bringing of the anvil roll and the ultrasonic horn together to form the bonding nip comprises lifting the anvil roll, thereby to bring the anvil roll into engaging relationship with the ultrasonic horn.
In preferred embodiments, the method includes pivoting the anvil roll about a third axis oriented perpendicular to the first axis thereby to attenuate any misalignment between the first axis and the second axis.
In some embodiments, the method includes limiting downward movement of the anvil loading assembly and thereby preventing disengagement of drive mechanism which in combination drives the anvil support apparatus and the horn support apparatus.
The method preferably includes adjusting height of the back-up roll and thereby controlling height of the back-up roll and the ultrasonic horn, in operation.
In some embodiments, the method includes releasing the support rolls and withdrawing the anvil roll, whereby the ultrasonic horn sags away from the back-up roll, and re-engaging the support rolls and thereby urging the anvil roll against the ultrasonic horn, and correspondingly urging the ultrasonic horn back into engagement with the back-up roll, whereby the ultrasonic horn is returned to the defined location.
In some embodiments, the method includes drawing workpiece segments across the anvil roll and through the nip defined between the anvil roll and the ultrasonic horn, at a speed of at least about 40 feet per minute, preferably at least about 600 feet per minute, and more preferably at least about 1000 feet per minute.
Preferred embodiments also generally include utilizing the load cell to detect and manage forces generated between the ultrasonic horn and the anvil roll.
Generally, workpiece segments to be bonded each have a thickness of up to about 0.25 inch.
In preferred embodiments, the frame, the anvil support apparatus, and the horn support apparatus collectively define a support structure which provides support sufficiently rigid that the ultrasonic horn and the anvil roll can be brought together, with optional interference between the horn and the anvil roll of no more than about 0.003 inch, in combination with defining sufficient nip pressure to develop ultrasonic bonds in the absorbent article workpiece segments passing through the nip.
In preferred embodiments, deflection of the composite of the support structure is no more than about 0.003 inch.
Preferred embodiments also generally include defining a nip width between the ultrasonic horn and the anvil roll, and applying force between the ultrasonic horn and the anvil roll, at the nip, corresponding to at least about 400 pounds per inch width of the nip.
In preferred embodiments, the method includes a controller controlling operation of the ultrasonic bonding apparatus, and outputting from the load cell, to the controller, information sufficient to enable the controller to provide suitable guidance for adjusting the closure apparatus to effect suitable bonding at the nip.
Preferably, the method includes adjusting force in the nip in response to the information received from the load cell.
In a fourth family of embodiments, the invention comprehends a method of creating ultrasonic bonds in sequentially advancing absorbent article workpiece segments. The method comprises passing the absorbent article workpiece segments through a bonding nip defined by an anvil roll and a rotary ultrasonic horn, activating ultrasonic energy to the horn, and creating ultrasonic bonds in workpiece segments passing through the nip, and using a load cell to detect forces representative of forces exerted on the horn or the anvil roll at the nip. The horn and anvil roll are supported by a frame, anvil support apparatus, defining an anvil loading assembly connected to the frame and supporting an anvil roll having an operating width and a circumference and mounted for rotation about a first axis, horn support apparatus connected to the frame and supporting the rotary ultrasonic horn mounted for rotation about a second axis, substantially aligned with the first axis, and closure apparatus adapted to bring the anvil roll and the ultrasonic horn together to form the bonding nip. A load cell support member is connected to the frame, and the load cell is mounted to the load cell support member such that force representative of force exerted on one of the ultrasonic horn and the anvil roll at the nip is detected by the load cell. The method optionally comprises bringing a back-up roll into engagement with an outer working surface of the ultrasonic horn. The method includes rotating the ultrasonic horn and anvil roll in common with each other and with movement of the workpiece segments through the nip, and thereby applying pressure to the workplace segments and correspondingly creating ultrasonic bonds in the workpiece segments passing through the nip.
In preferred embodiments, the method includes outputting information from the load cell and adjusting force in the nip in response to the information received from the load cell.